JP2003211500A - Mold for molding plastic lens and method for molding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for molding with a simple structure which does not deteriorate a rotary symmetry of an optical surface without excessively increasing a length of a molding cycle and to provide a method for molding. <P>SOLUTION: The mold for molding the plastic lens molds a circular concave lens as seen from an optical axis direction from a periphery at a center of an optical axis. The mold comprises one gate provided on the periphery of the lens for injecting a molten thermoplastic resin in a cavity formed of the mold, a plurality of resin reservoirs provided at the outside of the periphery of the lens as seen from the optical axis direction at positions of a lateral symmetry in an opposite direction to the gate with the optical axis center as a reference and at a virtual line for connecting the center of the optical axis to the gate, and a plurality of resin reservoir gates provided between the resin reservoir and the periphery of the lens. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die and an injection molding method for a plastic lens such as a projection lens for a projection television or a projector and a zoom lens for a video camera. In particular, the present invention relates to an injection mold and an injection molding method for a plastic lens for the purpose of improving the optical performance of the plastic lens.

[0002]

2. Description of the Related Art Recently, in projection lenses for projection televisions and projectors, and zoom lenses for video cameras, aspherical surfaces have been used in order to achieve higher precision by reducing aberrations, reduce the number of lenses, and reduce size and cost. Optical systems that incorporate lenses are commonly used.

Concerning the formation of this aspherical lens, it is difficult to form it by the glass polishing method of polishing the glass material of glass, and the processing cost becomes high in the glass molding method of compression molding the preformed glass material. Moreover, since it is practically applicable only to a lens having a small diameter of about 20 to 30 mm or less, a method of molding a plastic lens by a molding die is often used.

In particular, in the injection molding method in which a molten thermoplastic resin such as acrylic resin is filled into the cavity from the gate through a spool and a runner, and is cooled and solidified to form a predetermined optical surface shape, a molding die is used. This is a general method for molding a plastic lens, since a large-diameter aspherical lens having a diameter of 50 mm to 100 mm can be obtained with stable quality in a large amount at a low cost by transferring the cavity shape.

However, in the case of a lens having a difference in thickness between the central portion of the optical surface and the peripheral portion of the optical surface, for example, a concave lens, when the molten resin is filled from the gate provided in the peripheral portion of the optical surface, immediately after passing through the gate. The thickness difference between the lens center side and the lens peripheral side from the gate to the lens optical axis center is small, and the lens peripheral side has a large contact area with the cavity wall surface of the mold, which has high flow friction resistance and solidification speed. Is faster, the front end of the flow of the molten resin is closer to the center side of the lens than to the peripheral side of the lens. On the contrary, from the time when the flow front of the molten resin passes near the center of the optical axis of the lens, the peripheral portion of the lens with a large wall thickness has less flow resistance than the center portion of the lens with a small wall thickness, and the solidification speed is high. Since the speed is slower, the speed becomes faster in the peripheral portion of the lens, and therefore the flow front of the molten resin precedes.

Therefore, in the peripheral portion of the optical surface, which is the final filling position in the direction opposite to the gate, the flow fronts of the molten resin on the peripheral portions of the left and right optical surfaces are 90 degrees with the virtual line connecting the center of the optical axis and the gate as the axis of symmetry. Weld lines are likely to occur because they join at an angle of more than 4 degrees. Especially in lens molding, it is common to reduce the filling speed in order to reduce birefringence caused by residual stress and avoid jetting defects near the gate. It is low and the probability of becoming a weld line is high. The weld line is a ridge line extending from the outer peripheral side of the lens toward the inner peripheral side of the peripheral portion of the optical surface, and the optical surface shape changes, so that the optical performance is significantly deteriorated.

Further, the flow of the molten resin on the central side of the lens is
When the molten resin from the optical surface peripheral part merges after the molten resin from the optical surface peripheral part reaches the final filling position when the molten resin from the optical surface peripheral part side is significantly slower than the final filling position, Air inside the mold cannot escape from the provided gas vent, and air bubbles may be generated on the peripheral side of the optical surface near the final filling position after molding.

Therefore, in order to solve the above problems of the molding die and molding method for the plastic lens, a plastic lens and an optical device using the plastic lens described in JP-A-11-194203 have been proposed. In the plastic lens and the optical device using the plastic lens described in JP-A-11-194203, a spacer portion having a predetermined length in a direction along the optical axis direction of the lens surface is provided on the side surface side of the lens surface. By partially forming along the outer periphery of the lens surface at an axially symmetric position with the imaginary line connecting the gate and the center of the lens surface as the axis of symmetry, the molten resin that wraps around the lens periphery and collides with each other. , A plastic lens that can improve the precision of the lens surface by preventing the streak-like weld line that occurs from the surroundings toward the optical axis from the surroundings, and the optical equipment that uses this plastic lens. It has been proposed, and the content is mainly intended to be applied to board cameras.

[0009]

However, the structure of the plastic lens and the optical device using the plastic lens described in Japanese Patent Application Laid-Open No. 11-194203 has the following four problems.

First, as a first problem, since the spacer is provided in the optical axis direction, the thickness of the peripheral portion where the spacer is provided is further increased, and this portion of the maximum thickness is the rate-determining factor for cooling. However, there is a problem in that the productivity becomes longer and the productivity deteriorates.

A second problem is that since the spacer itself is large, the molecular orientation is different between the portion where the spacer is provided and the portion where the spacer is not provided due to the difference in the flow of the molten resin in the filling process and the holding pressure. Due to the difference in the solidification shrinkage state of the resin in the cooling process, a difference occurs in the optical surface shape when taken out from the mold after molding. Therefore, there arises a problem that the accuracy of the shape of the optical surface having rotational symmetry about the optical axis is deteriorated, or the lens cannot be molded for applications requiring shape accuracy.

As a third problem, since the spacer portion provided in the optical axis direction is integrated with the lens product shape,
When the optical axis of each lens is incorporated into a lens barrel of various image pickup systems such as a video camera having a plurality of lenses or a projection system for a projector, the distance between the lenses becomes large and the lens cannot be incorporated. The problem occurs. Further, when the spacer is projected to the outside of the lens outer diameter, it becomes more difficult to attach the spacer to the cylindrical lens barrel.

As a fourth problem, a spacer is provided in the thickness direction in the lens outer peripheral position in the vicinity of the gate in the embodiment of the invention described above. However, in the range from the vicinity of the gate to the center of the lens optical axis, the spacer on the center side is formed. Since an unbalanced flow occurs in which the flow front is further ahead of the peripheral side, there is a possibility that molding defects such as bubble generation due to air entrainment may occur.

In view of the above problems, it is an object of the present invention to provide an injection molding die and an injection molding method in which a concave lens made of plastic does not generate bubbles due to weld or air entrainment, without excessively lengthening the molding cycle. An optimum molding die and molding method that does not deteriorate the rotational symmetry of the optical surface and does not have a restriction on the distance between the lens surfaces in the optical system of a plurality of lenses and can be easily assembled in the lens barrel. Is provided at a low cost with a simple configuration.

[0015]

[Means for Solving the Problems] In order to solve the above problems,
The molding die of the plastic lens of the present invention is an injection molding die for forming a concave lens having a central part of the optical axis thinner than the peripheral part and seen from the optical axis direction,

One gate provided in the peripheral portion of the lens for injecting the molten thermoplastic resin into the cavity formed by the molding die,

With respect to the optical axis center, a direction opposite to the gate, and symmetrical with an imaginary line connecting the optical axis center and the gate as a symmetry axis, the lens peripheral portion of the lens peripheral portion when viewed from the optical axis direction. A plurality of resin reservoirs provided on the outside,

It is characterized in that a plurality of resin pool gates are provided between the resin pool portion and the lens peripheral portion.

Since the resin reservoir is provided at the filling position after the flow front on the lens peripheral side has passed the center of the optical axis leading from the lens center side, the imbalance of the filling pattern is appropriately improved and the final filling is performed. Welds and bubble defects at the position can be eliminated. Further, since the resin reservoir is provided not on the lens thickness direction but on the outer peripheral side, the thickness of the lens peripheral portion is not increased and the molding cycle is not lengthened. Further, the resin pool gate can minimize the flow into the resin pool and the influence of cooling, and can suppress the deterioration of the rotational symmetry of the optical surface shape of the lens.

Further, after molding, by cutting the lens-side root of the resin reservoir gate portion and removing the resin reservoir portion, it becomes similar to a conventional circular concave lens, and there is a problem in assembling into a lens barrel. There is no such thing. In addition, a new effect can be expected in that the resin pool is effectively used as a receiving portion for the ejection pin when the lens molded product is taken out from the molding die.

In the molding die of the present invention, the resin reservoir portion is located at a position 13 from the gate with respect to the optical axis center.
It is preferably at a position of 5 degrees or more.

When the resin reservoir is provided on the gate side, the resin reservoir is filled early and the effect of suppressing the subsequent flow of the molten resin on the lens peripheral side having a small flow resistance is small. By providing the resin reservoir at a position more than 135 degrees from the gate with respect to the center of the optical axis, the molten resin on the lens peripheral side enters the resin reservoir in a timely manner, so that the flow front on the lens peripheral side moves to the lens center. It is possible to effectively suppress the leading from the side and prevent the weld from being generated at the final filling position.

Further, in the molding die of the present invention, it is preferable that the direction of the resin reservoir gate is substantially parallel to an imaginary line connecting the gate and the optical axis center.

As described above, by providing the resin pool gate in a direction substantially parallel to the virtual line connecting the gate and the optical axis center, that is, in a direction substantially parallel to the resin flow direction, the flow resistance is increased. It is possible to suppress the occurrence of hesitation when the flow of the molten resin on the peripheral side of the lens, which is low, flows into the resin pool gate having high flow resistance.

Further, in the molding die of the present invention, it is preferable that the resin pooling gate is provided at a central portion of the lens peripheral portion in the plate thickness direction.

In general, the gate is provided near the optical surface of the lens, that is, at the end of the lens peripheral portion in the plate thickness direction in order to prevent jetting due to the flow front of the molten resin being separated from the mold surface. However, since the resin pool gate is provided in the central portion of the lens peripheral portion in the plate thickness direction as in the present invention, the molten resin whose temperature at the center of the thickness is high and which has low viscosity and is easy to flow is Because it flows into the pool gate,
When it flows into a resin pool gate with high flow resistance, it can prevent hesitation and also widen the distance between the lens optical surface and the resin pool gate. The effect of reducing the influence of the pool on the optical surface shape can be expected.

Further, in the molding die of the present invention, a gas vent is provided in the peripheral portion of the lens opposite to the gate with respect to the resin reservoir and the center of the optical axis, and a gas vent passage provided in the resin reservoir. It is preferable that the cross-sectional area is larger than the cross-sectional area of the passage of the gas vent provided in the peripheral portion of the lens.

The air in the cavity is pushed by the molten resin flowing in from the gate and is discharged to the outside of the mold through the gas vent, but the gas vent provided in the peripheral portion of the lens opposite the gate with respect to the center of the optical axis. The cross sectional area of the gas vent provided in the resin reservoir is larger than the cross sectional area of the resin reservoir, so that the resin reservoir has a lower internal air pressure resistance and a higher flow resistance than the lens side. It is possible to suppress hesitation when flowing into the resin pool gate.

Further, in the molding die of the present invention, it is preferable that the gas vent provided in the resin reservoir is provided with suction means for sucking air inside the die.

A suction means for sucking the air inside the mold is provided in the gas vent provided in the resin reservoir, suction is started when the molten resin reaches the resin reservoir gate, and the resin is filled in the resin reservoir. By the molding method of stopping the suction by (2), it is possible to suppress the occurrence of hesitation when flowing into the resin pool gate having a high flow resistance.

Further, the molding die of the present invention is provided with a mechanism for controlling the movement of the die so that the cross-sectional area of the passage of the resin pool gate is increased at the start of filling and becomes smaller after the completion of filling. The gate is provided with a mechanism for increasing the cross-sectional area of the passage by the amount of compression of the molten thermoplastic resin, closing the mold, filling the thermoplastic resin, and moving the mold by the amount of compression after filling is completed. Preferably.

In the case of flowing into the resin pool gate having a high flow resistance by controlling the movement of the mold so that the cross-sectional area of the resin pool gate is increased at the start of filling and the channel cross-sectional area is reduced after the filling is completed. In addition, it is possible to suppress the occurrence of hesitation and to reduce the deterioration of the rotational symmetry of the surface shape due to the resin pool in the cooling and solidifying process of the resin after the filling is completed.

Next, the method for molding a plastic lens of the present invention is characterized by being a molding method using the molding die for a plastic lens according to any one of claims 1 to 8.
With this configuration, the effects described above can be expected in the method of molding a plastic lens.

In the molding method of the present invention, suction is started using the suction means from the time when the molten thermoplastic resin passes through the resin pool gate, and the molten thermoplastic resin is collected in the resin pool portion. It is preferable to stop suction at the time of filling.

In the molding method of the present invention, the plastic molding die is closed by increasing the cavity volume by a predetermined compression amount before starting the filling of the molten thermoplastic resin so that the thermoplastic resin is completely sealed. It is preferable that the mold is moved by the amount corresponding to the compression to compress the thermoplastic resin filled in the cavity to form a predetermined lens shape.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION First and second embodiments of a plastic lens injection molding die and molding method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view and a side view of an injection molding die for a plastic lens according to the first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the injection molding die for the plastic lens according to the first embodiment of the present invention, showing the state of starting the filling.

FIG. 3 is a sectional view of the plastic lens injection molding die according to the first embodiment of the present invention in a closed state.

FIG. 4 is a filling pattern diagram showing the flow of resin in the injection molding die of the plastic lens in the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of a plastic lens injection molding die according to the second embodiment of the present invention in a closed state.

(Embodiment 1) First, a plastic lens injection molding die and a molding method according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the plastic lens 1
Is a concave aspherical lens which is circular when viewed from the optical axis direction and whose peripheral portion is thicker than the central portion, and is injection-molded by a molding die 2 shown in FIG. 2 using thermoplastic transparent acrylic resin for optics as a material. Formed by.

The molding die 2 has a structure in which movable side and fixed side insert dies 4a and 4b having lens shapes engraved on the movable side and fixed side mold bases 3a and 3b are fitted respectively, and water or the like is used. Temperature control grooves 18a and 18b for cooling the molding die 2 through the temperature cooling medium are provided. Further, in order to support injection compression molding in which the cavity volume is increased by a predetermined compression allowance and the mold is closed, and after filling, the mold is moved by the compression allowance to form a predetermined shape, the fixed-side mold base 3b is , The mold base 3b is slidable in the mold opening / closing direction.
The driving is controlled by a mold clamping mechanism 15 different from the mold clamping mechanism 14 of a.

In order to fill the molten thermoplastic resin from a molding machine (not shown), the molding die 2 is provided with a spool 12 and a runner 13, and the tip of the runner 13 is a side surface of the lens peripheral portion 10. In addition, in order to prevent the flowing tip of the molten resin from separating from the mold surface and causing jetting,
The gate 5 is provided on the same surface as the optical surface.

The resin reservoirs 6a and 6b shown in FIG. 1 are bilaterally symmetrical with respect to the optical axis center 11 at a position of 135 degrees or more from the gate 5 with an imaginary line connecting the optical axis center 11 and the gate 5 as a symmetrical axis. Moreover, the lens peripheral portion 10 when viewed from the optical axis direction
Are provided on the outside of the
The lens peripheral portion 1 is provided between a and 6b and the lens peripheral portion 10.
The resin pool gates 7a and 7b are provided in a direction substantially parallel to an imaginary line connecting the gate 5 and the optical axis center 11 at the center of the plate thickness direction of 0.
Is provided.

A gas vent 8 for letting air inside the cavity escape from the molding die 2 to the outside of the lens peripheral portion 10 of the insert dies 4a and 4b opposite to the gate 5 with the optical axis center 11 as a reference. Insert mold 4a, 4b
Is provided along the parting surface of the molding die 2 so as to be connected to the mold bases 3a and 3b, and similarly, the gas vents 9a and 9b for resin reservoirs provided in the resin reservoirs 6a and 6b are cut off. The area is larger than that of the gas vent 8.

The operation and effect of the plastic lens injection molding die and molding method according to the first embodiment of the present invention described above will be described below.

After the mold bases 4a and 4b are closed by the mold clamping mechanism 14, the mold base 4b is moved to the mold base 4a side by a predetermined compression margin by the mold clamping mechanism 15 to move the lens as shown in FIG. Increase the cavity volume of the molded part. In this case, since the lengths of the resin pooling gates 7a and 7b in the optical axis direction also increase, the passage cross-sectional area increases.

Next, the thermoplastic resin melted from the molding machine (not shown) is passed through the spool 12 and the runner 13,
It flows from the gate 5 into the concave lens portion.

As shown in FIG. 4, immediately after passing through the gate 5, the difference in thickness between the lens center side toward the optical axis center 11 from the gate 5 and the lens peripheral side is small, and the lens peripheral side is the insert mold 4a. Since the contact area with the wall surface of 4b is large, the flow frictional resistance is high, and the solidification speed is high, the front end of the molten resin flows closer to the lens center side than to the lens peripheral side. Further, from the time when the flow front of the molten resin passes near the optical axis center 11, the lens peripheral portion having a large wall thickness has less flow resistance and the solidification speed is slower than the lens central portion having a small wall thickness. Therefore, since the speed becomes faster in the peripheral portion of the lens, the flow front of the molten resin precedes.

However, the molten resin in the peripheral portion of the preceding lens passes through the resin reservoir gates 7a and 7b, and the resin reservoir portion 6
Since it flows into a and 6b, the velocity of the flow front at the lens peripheral part becomes slower, and at the final filling position, it arrives at an angle of 90 degrees or less almost at the same time as the flow front at the lens center side. Moreover, since the air inside the cabty escapes from the gas vent 8 to the outside of the molding die 2,
No bubble defects occur.

As described above, since the resin reservoirs 6a and 6b are provided at the filling position after the passage of the optical axis center 11 in which the flow front on the lens peripheral side precedes the lens center side, the imbalance of the filling pattern is appropriately performed. It is possible to improve and to eliminate weld and bubble defects at the final filling position. In particular, the three-dimensional resin flow analysis by the finite element method is applied to the first embodiment of the present invention, and the results are calculated by changing the position of the resin pool, and the resin pool is gated with the optical axis center as a reference. 5 to 135 degrees or more, preferably 135
By providing it at a position of 165 degrees to 165 degrees, the molten resin on the lens peripheral side enters the resin reservoirs 6a and 6b in a timely manner,
It is possible to effectively prevent the flow front end on the lens peripheral side from advancing ahead of the lens center side, and to prevent the weld from being generated at the final filling position.

Further, in the first embodiment of the present invention, since the resin reservoirs 6a and 6b are provided on the outer peripheral side of the concave lens 1, the peripheral wall of the lens does not become thick and the molding cycle becomes long. There are no disadvantages. In addition, a resin pool gate 7a, between the resin pool portions 6a, 6b and the concave lens 1,
By interposing 7b, the adverse effect of the addition of the resin reservoirs 6a and 6b is minimized and the rotational symmetry of the optical surface shape of the concave lens 1 is not deteriorated. After molding, by cutting the lens-side roots of the resin pooling gates 7a, 7b and removing the resin pooling portions 6a, 6b, there is no demerit such as a long interplanar distance in assembling into the lens barrel.

Further, the resin pooling gates 7a, 7b are arranged in a direction substantially parallel to an imaginary line connecting the gate 5 and the optical axis center 11, that is, in a direction substantially parallel to the flow direction of the molten resin.
And the resin pooling gates 7a and 7b are provided at the center portion of the lens peripheral portion 10 in the plate thickness direction, so that the temperature can be smoothly increased along the flow of the resin and at the high temperature and low temperature on the thickness center side. Molten resin that flows easily due to viscosity has high flow resistance,
Since it flows into the resin puddle gates 7a and 7b, which are difficult to flow, the molten resin on the peripheral side of the lens, which originally has a low flow resistance, can be filled in the resin puddle portions 6a and 6b without causing hesitation. Since the distance between the resin pool gates 7a and 7b is increased, it is possible to reduce the influence of the resin pool portions 6a and 6b on the optical surface shape when the resin is cooled and solidified. In addition, the lens peripheral part 1
The resin reservoir gas vents 9a, 9b provided in the resin reservoir have a larger passage sectional area than the gas vent 8 provided in the resin reservoir portion 0, so that the resin reservoirs 6a, 6b have a concave lens 1 shape. Compared with the above, it is possible to suppress the occurrence of hesitation, since the pressure resistance of the internal air is reduced.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention. As shown in FIG. 5, a suction device 16 composed of a pump or the like for sucking air in the cavity is provided in the resin pool gates 7a and 7b.
7a and 17b are connected, and suction is started when the molten resin reaches the resin pool gate, and suction is stopped when the resin pool is filled with the molding method.
Furthermore, it becomes easier to flow into the resin reservoirs 6a and 6b,
It is possible to prevent welds and bubble generation.

After the completion of the filling, the mold clamping mechanism 14 moves the movable mold base 3a and the movable insert mold 4a integrally by a predetermined compression allowance expanded before the start of the filling. The filled resin is compressed, but at the same time, the molding die 2 is moved so as to reduce the passage sectional area of the resin pooling gates 7a and 7b. Therefore, by widening the passage cross-sectional area of the resin pool gates 7a and 7b during filling, it becomes easier to flow into the resin pool portions 6a and 6b, and it becomes possible to prevent welds and air bubbles from being generated. In the process of cooling and solidifying the resin after completion of the filling, deterioration of the rotational symmetry of the surface shape due to the resin pool can be reduced.

In the first and second embodiments of the present invention, the lens shape is a concave lens on both sides.
The present invention is not limited to this, and the same effect can be obtained for a concave lens such as a meniscus type concave lens whose periphery is thicker than the center.

[0059]

As described above, the injection molding die of the present invention has a virtual direction that is opposite to the gate for injecting the molten thermoplastic resin based on the optical axis center and that connects the optical axis center and the gate. At the symmetrical position with the line as the axis of symmetry,
A plurality of resin reservoirs are provided outside the lens peripheral portion when viewed from the optical axis direction, and a plurality of resin reservoir gates are provided between the resin reservoir portion and the lens peripheral portion. Therefore, the imbalance of the filling pattern can be appropriately improved, the weld and the bubble defect at the final filling position do not occur, the wall thickness of the peripheral portion of the lens is not increased, and the molding cycle is not lengthened. In addition, it is possible to minimize the influence of the flow to the resin reservoir and cooling, and to suppress the deterioration of the rotational symmetry of the optical surface shape of the lens. Therefore, with the configuration of the present invention, it is possible to realize a plastic injection-molded concave lens that does not cause welds or bubble defects in a short molding cycle, with high accuracy, and in a shape that can be easily incorporated into the lens barrel without restriction.

Further, according to the molding method of the present invention, a plastic injection molding concave lens free from welds and bubble defects can be molded in a short molding cycle with high accuracy and a shape that can be easily incorporated into the lens barrel without restriction. You can

[Brief description of drawings]

FIG. 1 is a plan view (a) and a side view (b) of an injection molding die for a plastic lens according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a filling start state of an injection mold for a plastic lens according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the injection-molding die for the plastic lens according to the first embodiment of the present invention in a closed state.

FIG. 4 is a filling pattern diagram showing a flow of resin in an injection molding die for a plastic lens according to the first embodiment of the present invention.

FIG. 5 is a sectional view of a plastic lens injection-molding die according to a second embodiment of the present invention in a closed state.

[Explanation of symbols]

1 concave lens 2 Mold 3a, 3b Mold base 4a, 4b Insert mold 5 gates 6a, 6b resin reservoir 7a, 7b Resin accumulation gate 8 gas vents 9a, 9b Resin reservoir gas vent 10 lens periphery 11 Optical axis center 12 spools 13 runners 14 Mold clamping mechanism 15 Mold clamping mechanism 16 Suction device 17a, 17b pipe 18a, 18b Temperature control groove

Continued front page    (72) Inventor Shinya Maruyama             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Masayoshi Takahashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takashi Uemura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4F202 AH74 AM36 AR12 CA11 CB01                       CK08 CK18 CK90 CP01 CP04                       CP06                 4F206 AH74 AM36 AR12 JA03 JN25                       JN26 JN33 JQ04 JQ81

Claims (10)

[Claims] 1. An injection molding die for forming a concave lens having a center portion of an optical axis thinner than that of a peripheral portion when viewed from the direction of the optical axis, which is melted in a cavity formed by the molding die. One gate provided in the peripheral portion of the lens for injecting the thermoplastic resin and bilaterally symmetric with respect to the optical axis center in a direction opposite to the gate and with an imaginary line connecting the optical axis center and the gate as a symmetry axis At a position of, a plurality of resin reservoirs provided outside the lens peripheral portion when viewed from the optical axis direction, and a plurality of resin reservoir gates provided between the resin reservoir and the lens peripheral portion. A molding die for a plastic lens, which is characterized by being provided. 2. The molding die for a plastic lens according to claim 1, wherein the resin reservoir is located at a position of 135 degrees or more from the gate with respect to the center of the optical axis. 3. The molding die for a plastic lens according to claim 1, wherein the direction of the resin pool gate is substantially parallel to an imaginary line connecting the gate and the center of the optical axis. 4. The molding die for a plastic lens according to claim 1, wherein the resin pooling gate is provided at a central portion of the peripheral portion of the lens in the plate thickness direction. 5. A gas vent is provided in a lens peripheral portion opposite to the gate with respect to the resin reservoir and the center of the optical axis, and a passage sectional area of the gas vent provided in the resin reservoir is provided in the lens peripheral portion. The plastic mold according to any one of claims 1 to 4, characterized in that it is larger than a passage cross-sectional area of the gas vent. 6. The molding die for a plastic lens according to claim 1, wherein the gas vent provided in the resin reservoir portion is provided with suction means for sucking air inside the mold. Type. 7. The passage cross-sectional area of the resin pool gate is
The mold is moved and controlled so that it greatly decreases at the start of filling and becomes small after completion of the filling, the size of the passage cross-sectional area of the resin pool gate is increased by the amount of compression of the molten thermoplastic resin, and the mold is closed. The molding die for a plastic lens according to any one of claims 1 to 6, further comprising a mechanism for filling the thermoplastic resin and moving the die by the compression amount after the filling is completed. 8. A method for molding a plastic lens, which comprises using the molding die for a plastic lens according to any one of claims 1 to 7. 9. The suction device according to claim 8, wherein suction is started using the suction means at a time point when the molten thermoplastic resin passes through the resin pool gate, and the molten thermoplastic resin is filled in the resin pool portion. A method of molding a plastic lens, characterized in that the suction is stopped at the point of time. 10. The plastic molding die according to claim 8, wherein the cavity volume is increased by a predetermined compression amount before the filling of the molten thermoplastic resin is started, and the mold is closed to completely seal the thermoplastic resin. After the filling, the die is moved by the compression amount to compress the thermoplastic resin filled in the cavity to form a predetermined lens shape.